2 x 7S1P (14S) 5AH Lipos for Infineon 48V 20A Controller

[zukster]

I was thinking about building some 14S Lipo packs to replace my Canadian Tire Yardworks packs. The Yardworks
have served well for a couple of years but they don't like the higher discharge rate I've subjected them to in 2S
and 3S packs on 36-63V(input) 63V Cap 20A Infineon controllers. The equivalent Lipo can handle this and will be
about 1/2 the weight. The Yardworks batteries also do not perform well when its below freezing.

I just read about the 14S chargers elsewhere on the forum, so what I thought would be ideal would be 2 x 7S1P
Lipo Packs. Then I don't have to assemble the cells myself and charging would be plug and play. 14S would be
14x3.7= 51.8 nominal and 14x4.2V=58.8V max, which is a good safety margin for the controllers 63V Caps. I
could do 3 x 5S1P packs for 15x3.7= 55.5 nominal and 15x4.2=63V max, and slightly undercharge, but I prefer
14S at 58.8V max for the better safety margin. The 3S Yardworks have always worked well because they never
come off the chargers higher than 61.5V.

I found these on the net. Does anyone know where to buy them or something similiar?

Found them here:

http://flytown.en.china.cn/selling-...-5C-charge-series-High-rate-lipo-battery.html

Flytown's web site: I can't even find them on Flytown's site.

http://www.flytown-batt.com/

2 x 7S1P packs would balance nicely on a slide-on seat post rack and you'd barely notice the weight.

 

[dogman dan]

7s seems a bit rare. I haven't seen them at Hobby King, but it can take a long time to check all. 8s and 6s would do the same thing though. That should be easy enough to find.

Also, depending on your needs, you might consider 6s x2 for a 12s pack. This allows the use of less expensive chargers if that matters to you. 50v hot off the charger, and just about the right top speed on many hubmotor kits to pedal along without needing big front chainrings. Right about 25 mph on a 2807 for instance.

 

[zukster]

7s seems a bit rare. I haven't seen them at Hobby King, but it can take a long time to check all. 8s and 6s would do the same thing though.

Blasphemy. That would be non-symmetric I'm not sure my bi-symmetric techy mind could deal
with that. Humm - but I only have one heart and its on the left side, so maybe I'll try to deal with it.

The thing is that with the 20 Amp 6 fet little infineon and Bafang rear SWXH, it really shines with
15S connected. Feels lethargic with 10S. Maybe I'll get two of the Turnigy 6S and one 8S and see
how it does at both 12S and 14S. Then I'll have a backup unit too, and it still won't break the bank.

Now BMS to consider...

 

[neptronix]

or get 5s + 5s + 4s. Those are common pack types, and honestly anything over 6s is going to have two balance connectors anyway, due to how the RC world works.

As for those batteries, they are quite unheard of

 

[zukster]

anything over 6s is going to have two balance connectors anyway

Good point - that breaks my plug an play rule. So does three packs though. Perhaps 2 x 6S is
the way to go for me. I have two bikes to do, so there is strength in numbers.

 

[Ykick]

anything over 6s is going to have two balance connectors anyway

Good point - that breaks my plug an play rule. So does three packs though. Perhaps 2 x 6S is
the way to go for me. I have two bikes to do, so there is strength in numbers.

I run both 15S and 12S, the later is my favorite for cost and simplicity. 12S performance ain't shabby with stock motor/controller and in my experience, nearly depleted 15S is roughly same voltage as 12S HOT off charger.

If you're doing a non-suspension bike 12S is probably best. My non-suspension rig can be somewhat scary (potholes) running HOT 15S speeds...

Tough decision, especially if you like speed. I like speed but only appropriate speed for conditions and equipment.

 

[zukster]

I run both 15S and 12S, the later is my favorite for cost and simplicity.

Much appreciate this input. Its exactly what I was thinking. Also, its not beyond me to reassemble
the packs if I really feel inclined. But that's work. 2 x 7S1P would be perfect. Maybe they'll be more
available later. Seems like the Lipo world is really taking off and there are more and more options
available every day.

 

[dogman dan]

Don't fret the symmetry, it's series connecting, not paralell. Only the size needs symmetry. Anything that adds up to 14s will work fine.

I was suprised how nice I found 12s, at least on a 2807 motor. Got just about a perfect 25 mph, which happens to match a very common mtb gearing for pedaling along. 48 tooth crank and 14 tooth freewheel. Same bike on 14 or 15s, and I have to hold the throttle back a hair, and that is a tiny bit of hassle compared to just riding with it cranked full on. Not an issue on short rides, but over 10 miles, riding full throttle is easiest.

You could try some 12s, and order some 8s packs later if you decide it's too slow, or not enough for a hill.

 

[Ykick]

Don't fret the symmetry, it's series connecting, not paralell. Only the size needs symmetry. Anything that adds up to 14s will work fine.

I was suprised how nice I found 12s, at least on a 2807 motor. Got just about a perfect 25 mph, which happens to match a very common mtb gearing for pedaling along. 48 tooth crank and 14 tooth freewheel. Same bike on 14 or 15s, and I have to hold the throttle back a hair, and that is a tiny bit of hassle compared to just riding with it cranked full on. Not an issue on short rides, but over 10 miles, riding full throttle is easiest.

You could try some 12s, and order some 8s packs later if you decide it's too slow, or not enough for a hill.

yes, yes and yes - forgot to mention my 26" wheel 12S bike is 2807 (I know it as 9x7) motor. Those are the speeds I see.

I'm now building a highend Cannondale (killer suspension, hydro brakes) and decided to use 12S configration. Of course, I can always adapt 15S to any of my bikes but I wanna keep this one compact, lightweight and 25MPH top speed (20 nominal) is about all I really need.

Actually, 'will probably phase out my 15S Lipo altogether since 12S also benefits controller caps, pre-charge spark and what-not...

 

[zukster]

You could try some 12s, and order some 8s packs later if you decide it's too slow, or not enough for a hill.

Will do. Now I'm looking at the possibility of using LVC boards for the packs to alert me
or cut off the controller power in the event of a naughty cell dropping way below the rest
before the main controller LVC kicks in. These packs are so cheap now that I don't know
if its worth the extra time and effort though. You can catch the bad cell after your ride
when you hook up the packs to charge/balance them with one of those smarter chargers
that displays all the individual cell voltages.

What are other thoughts on this?

Ideally, if you're going to try to monitor the packs better during a ride, it would be nice
to have lights that indicate a bad pack, or even a bad cell (like philf tried). I like using
the Canadian Tire Yardworks batteries in series because they have built-in BMS that turn
them off if there is a problem, plus they have a four light bar that tells you the approximate
charge left in a pack when you press the button. So if I'm using 3S and say 2 packs are
at 3 light bars and one pack is at 1 light bar, I know there is a problem with it. If 2 packs
are at 3 or 4 and one has NO lights on, then you know that the BMS cut it off. Its not
super accurate, but it works well enough in practice to know when its time to swap in
a new pack for a bad one. Even with the more expensive packs like Ping or the ones
ebike.ca sells, I'm not sure if you get this extra info, or if you just have to switch the
whole big pack.

 

[dogman dan]

the best cheap, easy way would be the cheap 6s low voltage buzzers. build the buzzer wiring into the series adapter and have that built into the bike. Then when you plug in each 6s section, you get monitoring of the 6s pack. Other monitors will look at cell level, but the buzzers aren't so bad. Mount the buzzers where you can see the lights, because the sound can't be relied on. Watch the lights primarily. flash blue 3.75 per cell. Flash red, stop. 3.5v.

Others will chime in now and insist you get the lipo lvc. It's better, but not mandatory. Size your pack right, and you never even see 3.75v much.

Size the pack right, and you may only need to look at total pack voltage while you ride to be plenty safe. If a pack is a stinker, no lvc is going to give it better cells.

 

[zukster]

Mount the buzzers where you can see the lights

Oooh - I didn't know they had lights too. That works for me. I still like the idea of
having the packs turn themselves off too. They're in series so effectively one pack turning
itself off disables the entire circuit. This would be nice for building a bike for a
someone else. Most userland ebikers probably view the whole pack as a single unit;
its either working or it isn't (note my clever use of a semi-colon there ) My scheme
here is only slightly harder to deal with. For a 3 battery setup, you just have to identify
when an individual pack is bad. Lets say one pack has a cell that is way lower then
the rest. Turn a red light on to alert the user that it is possibly bad (we know it might
need balancing, but joe-user just knows it has to be checked later. Then make the
charger simple so it indicates: (1) charged okay or (2) replace pack. So at this point
they order a replacement 45 dollar 6S pack, instead of a 500 dollar complete pack.

Maybe I'm oversimplifying, but you should get the idea. Maybe I'll see if an electronics
buddy of mine could help me build a cheap board that could do this - but I suspect it
won't be that cheap, as it will need a relay to cut off the main battery power, so that
defeats the whole purpose when the battery is only 45 dollars.

Maybe I'll see if I can adapt one of my my Yardworks BMS to a lipo for grins. Not sure
the BMS LVC will be appropriate since they're Lithium Manganese chemistry. I think
I have 3 dead YW batteries that are dead that I can play with. Or maybe I should get
a life :|

 

[dogman dan]

TP packs sells the balance board, and the lvc board. They supply the harder to get parts, and you get the rest and solder it.

It's a great system, but for easy enough for dummies like me, the buzzers can work.